1. Field of the Invention
The present invention relates to an outer rotor type motor/generator housed in an annular space defined between an engine side wall and a crank pulley fixed to an end of a crankshaft, and comprises a stator supported on the engine side wall and a rotor supported on the inner face of the peripheral wall of the crank pulley so as to face the outer periphery of the stator across an air gap.
2. Description of the Related Art
Because the heat generated in a stator coil when a motor is operated adversely affects its durability, Japanese Patent Application Laid-open No. 10-322974 discloses an arrangement in which external air is forcibly introduced into the motor housing by means of a cooling fan provided on the rotating shaft of the motor so as to cool the heated stator coil. This kind of problem with heat generation is present not only in motors but also in generators.
Automobile starter motors are usually attached to the outside of the engine block, but if the starter motor is housed in an internal space of a crank pulley provided on a crankshaft, the overall size of the engine can be reduced and, moreover, the kinetic energy of the automobile body can be recovered as electrical energy from regenerative braking by making the starter motor function as a generator when operating an engine brake.
However, when the starter motor is housed inside the crank pulley provided on the crankshaft, it is necessary to take care to prevent foreign matter scattered from the road surface from being sucked inside the starter motor. If the starter motor is completely covered so as to prevent any foreign matter from being sucked in, the circulation of air inside the crank pulley deteriorates, thereby disadvantageously degrading the cooling performance of the starter motor.
The present invention has been carried out in view of the above-mentioned circumstances, and it is an object of the present invention to simultaneously satisfy both the requirement for preventing any foreign matter from being ingested and the requirement for cooling when a motor/generator is housed inside the crank pulley of an engine.
In order to achieve the above-mentioned object, there is proposed an outer rotor type motor/generator housed in an annular space defined between an engine side wall and a crank pulley fixed to an end of a crankshaft, and comprising a stator supported on the engine side wall and a rotor supported on the inner face of the peripheral wall of the crank pulley so as to face the outer periphery of the stator across an air gap, wherein an air inlet passage is formed between the engine side wall and the edge of the peripheral wall of the crank pulley so as to provide communication between the annular space and the outside of the crank pulley, and cooling fan blades provided on a side wall of the crank pulley extend radially outwards from one end of the crankshaft to the peripheral wall of the crank pulley, coils of the stator are cooled by the air introduced into the annular space via the air inlet passage and the air is discharged to the outside by means of the cooling fan blades.
In accordance with the above-mentioned arrangement, when the crankshaft rotates, the rotor supported on the crank pulley and the stator supported on the engine side wall rotate relative to each other, thereby exhibiting the function of one of a motor and a generator, and as a result the stator coils generate heat. When the cooling fan blades provided on the side wall of the crank pulley rotate along with the rotation of the crankshaft, air is introduced into the annular space via the air inlet passage formed between the engine side wall and the edge of the peripheral wall of the crank pulley, and the air cools the heated coils of the stator until it is discharged from the annular space to the outside of the crank pulley by means of the cooling fan blades. This allows the coils of the stator to be cooled effectively while housing the motor/generator in the annular space formed between the crank pulley and the engine side wall and preventing contamination and damage due to ingestion of foreign matter.
The above-mentioned stator may comprise a plurality of cores and coils, the cores being positioned radially and each of the cores having a coil wound around it, the radially outer ends of each of the cores projecting in the circumferential direction so as to be close to each other and forming air passages between adjacent coils, with air circulating through the air passages.
In accordance with the above-mentioned arrangement, because the radial outer ends of the stator cores project in the circumferential direction so as to be close to each other, it becomes more difficult for the air introduced into the annular space via the air inlet passage to enter the air gap between the stator and the rotor, and it is possible to prevent any foreign matter from being trapped in this air gap, thereby damaging the stator and the rotor. Moreover, because air passages through which air circulates are formed between adjacent coils, the coils can be cooled effectively by circulating air through the passages.
A shield for covering the entrance of the above-mentioned air gap may be formed on an end face of the stator facing the above-mentioned air inlet passage.
In accordance with the above-mentioned arrangement, because the entrance of the air gap is covered with the shield formed on the end face of the stator facing the air inlet passage, it becomes more difficult for the air introduced into the annular space via the air inlet passage to enter the air gap between the stator and the rotor, and it is possible to prevent any foreign matter from being trapped in this air gap, thereby damaging the stator and the rotor.
A large number of projections or channels inclined towards the circumferential direction may are formed on the outer periphery of the stator facing the entrance and the exit of the above-mentioned air gap so that the air flows generated by these projections or channels prevent air from entering the above-mentioned air gap.
In accordance with the above-mentioned arrangement, because a large number of projections or channels inclined towards the circumferential direction are formed on the outer periphery of the stator facing the entrance and the exit of the air gap, when air on the outer periphery of the stator is rotated by being dragged by the rotation of the rotor, air flows in directions flowing out of the entrance and exit of the air gap can be generated by the action of the above-mentioned inclined projections or channels so effectively preventing any foreign matter present in the air from entering the air gap.
The chain cover 26 in embodiments corresponds to the engine side wall of the present invention, and the magnet 34 in the embodiments corresponds to the rotor of the present invention.